The invention relates to the field of wound healing. In particular, the invention relates to the production of a wound healing agent that is mitogenic for vascular endothelial cells and consequently is useful in promoting neovascularization (angiogenesis) and re-endothelialization of inner vascular surfaces. The invention provides methods and means for producing vascular endothelial cell growth factor by means of recombinant DNA technology.
Angiogenesis, i.e. the growth of new capillary blood vessels, is a process which is crucial to the proper healing of many types of wounds. Consequently, factors that are capable of promoting angiogenesis are useful as wound healing agents. Angiogenesis is a multi-step process involving capillary endothelial cell proliferation, migration and tissue penetration. A number of known growth factors, including basic and acidic fibroblast growth factor, transforming growth factor alpha and epidermal growth factor, are broadly mitogenic for a variety of cell types as well as being angiogenic and are, therefore, potentially useful in promoting tissue repair. Broad spectrum mitogenicity is desirable in many types of wound healing applications. There are, however, specific types of wound healing applications in which it would be desirable to have a more cell-specific mitogenic activity. For example, following vascular graft surgery, balloon angioplasty or to promote collateral circulation in post-myocardial infarction patients, it would be desirable to employ a wound healing agent incorporating a mitogenic factor having mitogenic activity that is highly specific for vascular endothelial cells since proliferation of other cell types along with endothelial cells could cause blockage and/or reduced blood flow. At present, no highly suitable mitogenic factor is widely available for this type of application.
Recently, a mitogen apparently specific for vascular endothelial cells was isolated from media conditioned by bovine folliculo stellate cells and its partial amino acid sequence determined (Gospodarowicz et al., PNAS (1989) 86(19):7311-7315; Ferrara and Henzel, BBRC (1989) 161(2):851-858). This factor appears to be a homodimer of two approximately 23 kD subunits. A partially homologous factor that is the mouse homolog of the bovine protein described by Gospodarowicz et al. and Ferarra et al. has also been isolated from the conditioned media of murine AtT20 cells (ATCC CCL 89) and its N-terminal amino acid sequence determined (Plouet et al., EMBO J. (1989) 8(12):3801-3806). Both factors have been demonstrated to have mitogenic activity for vascular endothelial cells and for none of the other cell types tested and are therefore useful in a number of types of wound healing applications. Unfortunately, it is not practical and economical to obtain commercial quantities of these factors by purification from their native sources.